Control apparatus



T. C. MAcKAY.

CONTROL APPARATUS. APPLICATION FILED JUNE'Q. 1919.

1,365,421, Patented Jan. 11, 1921.

WITNESSES: INVENTOR f W Thgas CMGC/Y Qy ATTORNEY UNITED STATES PATENTOFFICE.

THOMAS C. MAcKAY, 0F PITTSBURGH, PENNSYLVAN'IA, ASSIGNOR TO WESTING-HOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENN- SYLVANIA.

CONTROL APPARATUS.

Application filed June 9,

and it has special relation to liquid rheostats for governing theoperation of induction motors or other translating devices.

One object of my invention is to provide a liquid rheostat, theeffective specific or unit-volume resistance of which may be varied bypneumatic means in the form of a perforated member that is adapted toblow bubbles of air or other'suitable fluid upwardly through therheostat.

Viewed from another angle, the object of my invention is to effect asweeping of gas bubbles upwardly past the electrodes of a liquidrheostat to remove impurities in the solution and to carry away suchinjurious gases as may form at the surface of the liquid. 1

A further object of my invention is to provide an apparatus of thecharacter in question wherein 'the rate of formation of bubbles isrendered responsive to the current or the voltage of the'induction motoror other translating device to be governed by the rheostat, whereby thevolume and number of escaping bubbles corresponds to the isolation ofdifferently sized bodies of electrolyte, and the total resistance of therheostat is automatically varied to maintain a substantially constantcurrent or voltage for the translating device.

My invention may best be understood by reference to the accompanyingdrawings, wherein- Figure 1 is a diagrammatic view of a complete controlapparatus and system constructed and organized in accordance with thepresent invention; and

Fig. 2 and Fig. 3 are detail views, respectively in longitudinal and intransverse section, of a liquid'rheostat similar to that shown in planview in Fig. 1.

Referringto the drawing, the system here shown comprises an inductionmotor 1 having a primary stator winding 5 and a wound rotor 6 that-isconnected to a liquid rheostat .2, the operation of which is gov-Specification of Letters Patent.

Patented Jan. 11, 1921.

1919. Serial No. 302,710.

erned by means of a gas-venting apparatus 3 which is supplied from asuitable tank or reservoir 4 under conditions to be hereinafter morefully set forth.

The liquid rheostat 2 may, in general, be of any well-known constructionand comprises a tank or incasing member 7 which contains a body ofsuitable-electrolyte S for immersing a plurality of electrodes or plates9 corresponding to the three phases of the wound rotor 6 oft-he'induction motor 1. As is customary practice, four electrodes areprovided, the two intermediate electrodes being connected, throughconductors l0 and 11, to two of the collector rings of the rotor 6,while the two outer plates are connected together and communicate withthe remain ing collector ring of the rotor 6 through a conductor 12.

Near the bottom of the rheostat 2, my gasventing device 3 is located andcomprises a supply pipe or manifold 13 with which communicates aplurality of perpendicularly related pipes or tubes 15, 16 and 17, allof which are suitably perforated, as indicatedby the small circles. Therespective pipes 15, 16 and 17 are preferably located in the spacesbetween the adjacent pairs of electrodes 9. A suitable pipingarrangement 18 serves to effect communication between the manifold 13and the supply tank 4 of air pressure or other suitable fluid, a valve19 being interposed between the supply reservoir and the gas-ventingdevice 3.

The valve 19 may be of any suitable type and is shown as provided with amovable plug 20, to which a magnetizable core member 21 is secured,around which an actuating coil 22 is wound. The coil 22 is shown asconnected in series relation with the conductor 12, whereby the valveplug 20 is actuated upwardly or allowed to drop in accordance with thecurrent that traverses the corresponding phase of the wound rotor 6.However, it will be understood that, if desired, the coil 22 may beenergized in accordance with any other desired electrical condition,such as the primary or secondary voltage of the induction motor 1 orother translating device.

Neglecting for the moment the operation of the valve 19, it will benoted thatthe supply of air or other fluid under pressure to theperforated tubes 15, 16 and 17 forces bubbles or globules of suchvfluid. to sweep upwardly through the spaces between the electrodes 9.Such action corresponds to the isolation of differently proportionedbodies of electrolyte, and the total resistance provided by the rheostat2 is accordingly increased.

Not only is the specific or unit volume resistance of the electrolytebetween the plates thus varied, but, in addition, the followingadvantages obtained by the use of my control apparatus. The rate ofevaporation of the liquid and, consequently, the rate of removal of heatfrom the solution, is materially increased to prevent boiling and othersimilar undesirable effects of the assage of current through therheostat. urthermore, small bubbles of hydrogen or other gases thatordinarily cling to the surfaces of the electrodes, and which chemicallyattack the electrode material, are removed by the sweeping action of theupwardly-flowing air bubbles, whereby the life of the electrodes ismaterially prolonged. Moreover, impurities in the solution itself areremoved by flotation and bubbling, over of scum at the surface of theliquid through openings which may be provided in the sides of thecontaining vessel 7. In addition, if a continuous circulation ofelectrolyte is provided in accordance with any wellknown method, thepresent apparatus provides improved convection of heat, whereby asmaller and less expensive cooling apparatus, such as the familiarcooling coils, is permissible to provide a given degree of temperaturereduction. Also, any explosive gases or vapors injurious to health thatmay form at the surface of the liquid in the rheostat are automaticallycarried away by means of the escaping air bubbles.

Referring to the automatic control of the rate of bubbling by means ofthe valve 19, it will be understood that, whenever the current in therotor winding 6 increases, the core 21 is attracted upwardly by the coil22 to enlarge the air passage through the valve 19 and thus force agreater volume of gas through the perforations in the several tubes 15,16 and 17. Such increased rate of bubbling breaks up the electrolyteinto smaller isolated bodies and thereby increases the resistance of therheostat. Consequently, the current traversing the rotor winding 6 isagain reduced to normal, and the valve 19 is again allowed to drop to anaverage position. The converse action occurs in the event of a decreaseof the rotor current from the average value. In this way, the valve 19is automatically actuated in accordance with the current traversing therotor winding 6 to vary the resistance of the electrolyte in such manneras to maintain a substantially constant current in the rotor.

I do not wish to be restricted to the specific circuit connections,arrangement of parts or structural details herein set forth, as variousmodifications thereof may be made without departing from the spirit andscope of my invention. I desire, therefore, that only such limitationsshall be imposed as are indicated in the appended claims.

I claim as my invention 1. In a liquid rheostat, the combination with aplurality of electrodes, of pneumatic means for varying the specificresistance of the liquid between said electrodes.

2. In a liquid rheostat, the combination with a plurality of electrodes,of means for blowing a fluid through the liquid between said electrodesto vary the resistance of the rheostat.

3. In a liquid rheostat, the combination with a plurality of electrodes,of means for blowing bubbles of gas through the liquid between saidelectrodes to vary the resistance of the rheostat.

4. In a liquid rheostat, the combination with a plurality of electrodes,of means comprising a perforated member for effecting the passage of gasbubbles through the liquid.

5. In a liquid rheostat, the combination with a plurality of electrodes,of a perforated hollow member located below the electrodes, and meansfor forcing a gas through the perforations.

6. In a liquid rheostat, the combination with a plurality of electrodes,of means for causing air bubbles to sweep upwardly past said electrodes.

7. In a liquid rheostat, the combination with a plurality of spacedelectrodes, of a source of airpressure, and a plurality of perforatedtubular members communicating with said source and located in positionsto blow air upwardly through the spaces between the electrodes.

8. The combination with a translating device and a liquid rheostat forgoverning the operation thereof, of pneumatic means responsive tocertain electrical conditions of said translating device for varying thespecific resistance of the liquid in the rheostat.

9. The combination with a translating device and a liquid rheostat forgoverning the operation thereof, of means responsive to certainelectrical conditions of said translating device for blowing a fluidthrough the liquid in the rheostat to vary the resistance thereof.

10. The combination with a translating device and a liquid rheostat forgoverning the operation thereof, of means responsive to certainelectrical conditions of said translating device for blowing bubbles ofgas through the liquid in the rheostat to vary the resistance thereof.

11. The combination with a translating device and a liquid rheostat forgoverning the operation thereof, of means comprising a perforated memberfor effecting the passage of gas bubbles through the liquid, and meansresponsive to certain electrical conditions of said translating devicefor regulating the rate of formation of such bubbles.

12. The combination with a translating device and a liquid rheostat forgoverning the operation thereof, of a perforated hollow member locatednear the bottom of the rheostat, means for forcing a gas through theperforations, and a valve responsive to certain electrical conditions ofsaid translating device for regulating the rate of flow of such gas.

13. The combination with a translating device and a liquid rheostat forgoverning the operation thereof, said rheostat embodying a plurality ofspaced electrodes, of a source of air-pressure, a plurality ofperforated tubular members communicating with said source and located inpositions to blow air upwardly through the spaces between saidelectrodes, and a valve responsive to certain electrical conditions ofsaid trans lating device for varying the volume of air supplied to saidperforated members.

In testimony whereof, I have hereunto subscribed my name this 31st dayof May, 1919.

THOMAS C. MAOKAY.

